This invention relates generally to the structure of soles of shoes and other footwear, including soles of street shoes, hiking boots, sandals, slippers, and moccasins. More specifically, this invention relates to the structure of athletic shoe soles, including such examples as basketball and running shoes.
Still more particularly, this application explicitly includes an alternate definition of the inner surface of the theoretically ideal stability plane as being complementary to the shape of the wearer""s foot, instead of conforming to the wearer""s foot sole or to a shoe last approximating it either for a specific individual; such alternate definition is more like a standard shoe last that approximates the exact shape and size of the individual wearer""s foot sole for mass production. This application also includes the broadest possible definition for the inner surface of the contoured shoe sole sides that still defines over the prior art, namely any position between roughly paralleling the wearer""s foot sole and roughly paralleling the flat ground.
Still more particularly, in its simplest conceptual form, this invention relates to variations in the structure of such shoes having a sole contour which follows a theoretically ideal stability plane as a basic concept, but which deviates substantially therefrom outwardly, to provide greater than natural stability, so that joint motion of the wearer is restricted, especially the ankle joint; or, alternately, which deviates substantially therefrom inwardly, to provide less than natural stability, so that a greater freedom of joint motion is allowed. Alternately, substantial density variations or bottom sole designs are used instead of, or in combination with, substantial thickness variations for the same purpose. These shoe sole modifications are research indicating that they are necessary and useful to correct important interrelated anatomical/biomechanical imbalances or deformities of surprising large magnitude in both individuals or major population groups.
More particularly, in its simplest conceptual form, this invention is the structure of a conventional shoe sole that has been modified by having its sides bent up so that their inner surface conforms to a shape nearly identical but slightly smaller than the shape of the outer surface of the sides of the foot sole of the wearer (instead of the shoe sole sides conforming to the ground by paralleling it, as is conventional). The shoe sole sides are sufficiently flexible to bend out easily when the shoes are put on the wearer""s feet and therefore the shoe soles gently hold the sides of the wearer""s foot sole when on, providing the equivalent of custom fit in a mass-produced shoe sole.
Still more particularly, this invention relates to shoe sole structures that are formed to conform to the all or part of the shape of the wearer""s foot sole, whether under a body weight load or unloaded, but without contoured stability sides as defined by the applicant.
Still more particularly, this invention relates to variations in the structure of such soles using a theoretically ideal stability plane as a basic concept, especially including structures exceeding that plane.
Finally, this invention relates to contoured shoe sole sides that provide support for sideways tilting of any angular amount from zero degrees to 180 degrees at least for such contoured sides proximate to any one or more or all of the essential stability or propulsion structures of the foot, as defined below and previously.
The parent ""598 application clarified and expanded the applicant""s earlier filed U.S. application Ser. No. 07/680,134, filed Apr. 3, 1991.
The applicant has introduced into the art the concept of a theoretically ideal stability plane as a structural basis for shoe sole designs. The theoretically ideal stability plane was defined by the applicant in previous copending applications as the plane of the surface of the bottom of the shoe sole, wherein the shoe sole conforms to the natural shape of the wearer""s foot sole, particularly its sides, and has a constant thickness in frontal or transverse plane cross sections. Therefore, by definition, the theoretically ideal stability plane is the surface plane of the bottom of the shoe sole that parallels the surface of the wearer""s foot sole in transverse or frontal plane cross sections.
The theoretically ideal stability plane concept as implemented into shoes such as street shoes and athletic shoes is presented in U.S. Pat. No. 4,989,349, issued Feb. 5, 1991 and U.S. Pat. No. 5,317,819, issued Jun. 7, 1994, both of which are incorporated by reference; and pending U.S. application Ser. No. 07/400,714, filed Aug. 30, 1989; Ser. No. 07/416,478, filed Oct. 3, 1989; Ser. No. 07/424,509, filed Oct. 20, 1989; Ser. No. 07/463,302, filed Jan. 10, 1990; Ser. No. 07/469,313, filed Jan. 24, 1990; Ser. No. 07/478,579, filed Feb. 8, 1990; Ser. No. 07/539,870, filed Jun. 18, 1990; Ser. No. 07/608,748, filed Nov. 5, 1990; Ser. No. 07/783,145, filed Oct. 28, 1991; and Ser. No. 07/926,523, filed Aug. 10, 1992.
PCT applications based on the above patents and applications have been published as WO 90/00358 of Jan. 25, 1990 (part of the ""349 Patent, all of the ""819 Patent and part of ""714 application); WO 91/03180 of Mar. 21, 1991 (the remainder of the ""714 application); WO 91/04683 of Apr. 18, 1991 (the ""478 application); WO 91/05491 of May 02, 1991 (the ""509 application); WO 91/10377 of Jul. 25, 1991 (the ""302 application); WO 91/11124 of Aug. 08, 1991 (the ""313 application); WO 91/11924 of Aug. 22, 1991 (the ""579 application); WO 91/19429 of Dec. 26, 1991 (the ""870 application); WO 92/07483 of May 14, 1992 (the ""748 application); WO 92/18024 of Oct. 29, 1992 (the ""598 application); and WO 94/03080 of Feb. 17, 1994 (the ""523 application). All of above publications are incorporated by reference in this application to support claimed prior embodiments that are incorporated in combinations with new elements disclosed in this application.
This new invention is a modification of the inventions disclosed and claimed in the earlier applications and develops the application of the concept of the theoretically ideal stability plane to other shoe structures. Each of the applicant""s applications is built directly on its predecessors and therefore all possible combinations of inventions or their component elements with other inventions or elements in prior and subsequent applications have always been specifically intended by the applicant. Generally, however, the applicant""s applications are generic at such a fundamental level that it is not possible as a practical matter to describe every embodiment combination that offers substantial improvement over the existing art, as the length of this description of only some combinations will testify.
Accordingly, it is a general object of this invention to elaborate upon the application of the principle of the theoretically ideal stability plane to other shoe structures.
The purpose of the earlier ""523 application was to specifically describe some of the most important combinations, especially those that constitute optimal ones, that exist between the applicant""s U.S. patent application Ser. No. 07/400,714, filed Aug. 30, 1989, and subsequent patents filed by the applicant, particularly U.S. Ser. No. 07/416,478, filed Oct. 3, 1989, as well as some other combinations.
The ""714 Application indicated that existing running shoes are unnecessarily unsafe. They profoundly disrupt natural human biomechanics. The resulting unnatural foot and ankle motion leads to what are abnormally high levels of running injuries.
Proof of the unnatural effect of shoes has come quite unexpectedly from the discovery that, at the extreme end of its normal range of motion, the unshod bare foot is naturally stable, almost unsprainable, while the foot equipped with any shoe, athletic or otherwise, is artificially unstable and abnormally prone to ankle sprains. Consequently, ordinary ankle sprains must be viewed as largely an unnatural phenomena, even though fairly common. Compelling evidence demonstrates that the stability of bare feet is entirely different from the stability of shoe-equipped feet.
The underlying cause of the universal instability of shoes is a critical but correctable design flaw. That hidden flaw, so deeply ingrained in existing shoe designs, is so extraordinarily fundamental that it has remained unnoticed until now. The flaw is revealed by a novel new biomechanical test, one that is unprecedented in its simplicity. It is easy enough to be duplicated and verified by anyone; it only takes a few minutes and requires no scientific equipment or expertise. The simplicity of the test belies its surprisingly convincing results. It demonstrates an obvious difference in stability between a bare foot and a running shoe, a difference so unexpectedly huge that it makes an apparently subjective test clearly objective instead. The test proves beyond doubt that all existing shoes are unsafely unstable.
The broader implications of this uniquely unambiguous discovery are potentially far-reaching. The same fundamental flaw in existing shoes that is glaringly exposed by the new test also appears to be the major cause of chronic overuse injuries, which are unusually common in running, as well as other sport injuries. It causes the chronic injuries in the same way it causes ankle sprains; that is, by seriously disrupting natural foot and ankle biomechanics.
It was a general object of the ""714 invention to provide a shoe sole which, when under load and tilting to the side, deforms in a manner which closely parallels that of the foot of its wearer, while retaining nearly the same amount of contact of the shoe sole with the ground as in its upright state.
It was still another object of the ""714 invention to provide a deformable shoe sole having the upper portion or the sides bent inwardly somewhat so that when worn the sides bend out easily to approximate a custom fit.
It was still another object of the ""714 invention to provide a shoe having a naturally contoured sole which is abbreviated along its sides to only essential structural stability and propulsion elements, which are combined and integrated into the same discontinuous shoe sole structural elements underneath the foot, which approximate the principal structural elements of a human foot and their natural articulation between elements.
The ""478 invention relates to variations in the structure of such shoes having a sole contour which follows a theoretically ideal stability plane as a basic concept, but which deviates therefrom outwardly, to provide greater than natural stability. Still more particularly, this invention relates to the use of structures approximating, but increasing beyond, a theoretically ideal stability plane to provide greater than natural stability for an individual whose natural foot and ankle biomechanical functioning have been degraded by a lifetime use of flawed existing shoes.
The ""478 invention is a modification of the inventions disclosed and claimed in the earlier application and develops the application of the concept of the theoretically ideal stability plane to other shoe structures. As such, it presents certain structural ideas which deviate outwardly from the theoretically ideal stability plane to compensate for faulty foot biomechanics caused by the major flaw in existing shoe designs identified in the earlier patent applications.
The shoe sole designs in the ""478 application are based on a recognition that lifetime use of existing shoes, the unnatural design of which is innately and seriously flawed, has produced actual structural changes in the human foot and ankle. Existing shoes thereby have altered natural human biomechanics in many, if not most, individuals to an extent that must be compensated for in an enhanced and therapeutic design. The continual repetition of serious interference by existing shoes appears to have produced individual biomechanical changes that may be permanent, so simply removing the cause is not enough. Treating the residual effect must also be undertaken.
Accordingly, it was a general object of the ""478 invention to elaborate upon the application of the principle of the theoretically ideal stability plane to other shoe structures.
It was still another object of the ""478 invention to provide a shoe having a sole contour which deviates outwardly in a constructive way from the theoretically ideal stability plane.
It was another object of the ""478 invention to provide a sole contour having a shape naturally contoured to the shape of a human foot, but having a shoe sole thickness which is increases somewhat beyond the thickness specified by the theoretically ideal stability plane.
It is another object of this invention to provide a naturally contoured shoe sole having a thickness somewhat greater than mandated by the concept of a theoretically ideal stability plane, either through most of the contour of the sole, or at preselected portions of the sole.
It is yet another object of this invention to provide a naturally contoured shoe sole having a thickness which approximates a theoretically ideal stability plane, but which varies toward either a greater thickness throughout the sole or at spaced portions thereof, or toward a similar but lesser thickness.
The ""302 invention relates to a shoe having an anthropomorphic sole that copies the underlying support, stability and cushioning structures of the human foot. Natural stability is provided by attaching a completely flexible but relatively inelastic shoe sole upper directly to the bottom sole, enveloping the sides of the midsole, instead of attaching it to the top surface of the shoe sole. Doing so puts the flexible side of the shoe upper under tension in reaction to destabilizing sideways forces on the shoe causing it to tilt. That tension force is balanced and in equilibrium because the bottom sole is firmly anchored by body weight, so the destabilizing sideways motion is neutralized by the tension in the flexible sides of the shoe upper. Still more particularly, this invention relates to support and cushioning which is provided by shoe sole compartments filled with a pressure-transmitting medium like liquid, gas, or gel. Unlike similar existing systems, direct physical contact occurs between the upper surface and the lower surface of the compartments, providing firm, stable support. Cushioning is provided by the transmitting medium progressively causing tension in the flexible and semi-elastic sides of the shoe sole. The compartments providing support and cushioning are similar in structure to the fat pads of the foot, which simultaneously provide both firm support and progressive cushioning.
Existing cushioning systems cannot provide both firm support and progressive cushioning without also obstructing the natural pronation and supination motion of the foot, because the overall conception on which they are based is inherently flawed. The two most commercially successful proprietary systems are Nike Air, based on U.S. Pat. No. 4,219,945 issued Sep. 2, 1980, U.S. Pat. No. 4,183,156 issued Sep. 15, 1980, U.S. Pat. No. 4,271,606 issued Jun. 9, 1981, and U.S. Pat. No. 4,340,626 issued Jul. 20, 1982; and Asics Gel, based on U.S. Pat. No. 4,768,295 issued Sep. 6, 1988. Both of these cushioning systems and all of the other less popular ones have two essential flaws.
First, all such systems suspend the upper surface of the shoe sole directly under the important structural elements of the foot, particularly the critical the heel bone, known as the calcaneus, in order to cushion it. That is, to provide good cushioning and energy return, all such systems support the foot""s bone structures in buoyant manner, as if floating on a water bed or bouncing on a trampoline. None provide firm, direct structural support to those foot support structures; the shoe sole surface above the cushioning system never comes in contact with the lower shoe sole surface under routine loads, like normal weight-bearing. In existing cushioning systems, firm structural support directly under the calcaneus and progressive cushioning are mutually incompatible. In marked contrast, it is obvious with the simplest tests that the barefoot is provided by very firm direct structural support by the fat pads underneath the bones contacting the sole, while at the same time it is effectively cushioned, though this property is underdeveloped in habitually shoe shod feet.
Second, because such existing proprietary cushioning systems do not provide adequate control of foot motion or stability, they are generally augmented with rigid structures on the sides of the shoe uppers and the shoe soles, like heel counters and motion control devices, in order to provide control and stability. Unfortunately, these rigid structures seriously obstruct natural pronation and supination motion and actually increase lateral instability, as noted in the applicant""s pending U.S. applications Ser. No. 07/219,387, filed on Jul. 15, 1988; Ser. No. 07/239,667, filed on Sep. 2, 1988; Ser. No. 07/400,714, filed on Aug. 30, 1989; Ser. No. 07/416,478, filed on Oct. 3, 1989; and Ser. No. 07/424,509, filed on Oct. 20, 1989, as well as in PCT Application No. PCT/US89/03076 filed on Jul. 14, 1989. The purpose of the inventions disclosed in these applications was primarily to provide a neutral design that allows for natural foot and ankle biomechanics as close as possible to that between the foot and the ground, and to avoid the serious interference with natural foot and ankle biomechanics inherent in existing shoes.
In marked contrast to the rigid-sided proprietary designs discussed above, the barefoot provides stability at it sides by putting those sides, which are flexible and relatively inelastic, under extreme tension caused by the pressure of the compressed fat pads; they thereby become temporarily rigid when outside forces make that rigidity appropriate, producing none of the destabilizing lever arm torque problems of the permanently rigid sides of existing designs.
The applicant""s ""302 invention simply attempts, as closely as possible, to replicate the naturally effective structures of the foot that provide stability, support, and cushioning.
Accordingly, it was a general object of the ""302 invention to elaborate upon the application of the principle of the natural basis for the support, stability and cushioning of the barefoot to shoe structures.
It was still another object of the ""302 invention to provide a shoe having a sole with natural stability provided by attaching a completely flexible but relatively inelastic shoe sole upper directly to the bottom sole, enveloping the sides of the midsole, to put the side of the shoe upper under tension in reaction to destabilizing sideways forces on a tilting shoe.
It was still another object of the ""302 invention to have that tension force is balanced and in equilibrium because the bottom sole is firmly anchored by body weight, so the destabilizing sideways motion is neutralized by the tension in the sides of the shoe upper.
It was another object of the ""302 invention to create a shoe sole with support and cushioning which is provided by shoe sole compartments, filled with a pressure-transmitting medium like liquid, gas, or gel, that are similar in structure to the fat pads of the foot, which simultaneously provide both firm support and progressive cushioning.
These and other objects of the invention will become apparent from a detailed description of the invention which follows taken with the accompanying drawings.
This continuation-in-part application broadens the definition of the theoretically ideal stability plane, as defined in the ""786 and all prior applications filed by the applicant. The ""819 Patent and subsequent applications have defined the inner surface of the theoretically ideal stability plane as conforming to the shape of the wearer""s foot, especially its sides, so that the inner surface of the applicant""s shoe sole invention conforms to the outer surface of the wearer""s foot sole, especially it sides, when measured in frontal plane or transverse plane cross sections.
This new application explicitly includes an upper shoe sole surface that is complementary to the shape of all or a portion the wearer""s foot sole. In addition, this application describes shoe contoured sole side designs wherein the inner surface of the theoretically ideal stability plane lies at some point between conforming or complementary to the shape of the wearer""s foot sole, that isxe2x80x94roughly paralleling the foot sole including its sidexe2x80x94and paralleling the flat ground; that inner surface of the theoretically ideal stability plane becomes load-bearing in contact with the foot sole during foot inversion and eversion, which is normal sideways or lateral motion. The basis of this design was introduced in the applicant""s ""302 application relative to FIG. 9 of that application.
Additionally, this application describes shoe sole side designs wherein the lower surface of the theoretically ideal stability plane, which equates to the load-bearing surface of the bottom or outer shoe sole, of the shoe sole side portions is above the plane of the underneath portion of the shoe sole, when measured in frontal or transverse plane cross sections; that lower surface of the theoretically ideal stability plane becomes load-bearing in contact with the ground during foot inversion and eversion, which is normal sideways or lateral motion.
Although the inventions described in this application may in many cases be less optimal than those previously described by the applicant in earlier applications, they nonetheless distinguish over all prior art and still do provide a significant stability improvement over existing footwear and thus provide significantly increased injury prevention benefit compared to existing footwear.
In its simplest conceptual form, the applicant""s earlier invention disclosed in his ""714 application is the structure of a conventional shoe sole that has been modified by having its sides bent up so that their inner surface conforms to a shape nearly identical but slightly smaller than the shape of the outer surface of the foot sole of the wearer (instead of the shoe sole sides being flat on the ground, as is conventional). This concept is like that described in FIG. 3 of the applicant""s Ser. No. 07/239,667 application; for the applicant""s fully contoured design described in FIG. 15 of the ""667 application, the entire shoe solexe2x80x94including both the sides and the portion directly underneath the footxe2x80x94is bent up to conform to a shape nearly identical but slightly smaller than the contoured shape of the unloaded foot sole of the wearer, rather than the partially flattened load-bearing foot sole shown in FIG. 3.
In this continuation-in-part application, the use of this invention with otherwise conventional shoes with any side sole portion, including contoured sides with uniform or any other thickness variation or density variation, including bottom sole tread variation, especially including those defined below by the applicant, is further clarified.
This theoretical or conceptual bending up must be accomplished in practical manufacturing without any of the puckering distortion or deformation that would necessarily occur if such a conventional shoe sole were actually bent up simultaneously along all of its the sides; consequently, manufacturing techniques that do not require any bending up of shoe sole material, such as injection molding manufacturing of the shoe sole, would be required for optimal results and therefore is preferable.
It is critical to the novelty of this fundamental concept that all layers of the shoe sole are bent up around the foot sole. A small number of both street and athletic shoe soles that are commercially available are naturally contoured to a limited extent in that only their bottom soles, which are about one quarter to one third of the total thickness of the entire shoe sole, are wrapped up around portions of the wearers"" foot soles; the remaining soles layers, including the insole, midsole and heel lift (or heel) of such shoe soles, constituting over half of the thickness of the entire shoe sole, remains flat, conforming to the ground rather than the wearers"" feet. (At the other extreme, some shoes in the existing art have flat midsoles and bottom soles, but have insoles that conform to the wearer""s foot sole.)
Consequently, in existing contoured shoe soles, the total shoe sole thickness of the contoured side portions, including every layer or portion, is much less than the total thickness of the sole portion directly underneath the foot, whereas in the applicant""s prior shoe sole inventions, including the ""819 Patent and ""714 and ""478 application, as well as the applicant""s other pending applications, the shoe sole thickness of the contoured side portions are the same as the thickness of the sole portion directly underneath the foot, meaning uniform thickness as measured in frontal or transverse plane cross sections, or at least similar to the thickness of the sole portion directly underneath the foot, meaning a thickness variation of up to 25 percent, as measured in frontal or transverse plane cross sections.
This continuation-in-part application explicitly defines those thickness variations, as measured in frontal or transverse plane cross sections, of the applicant""s shoe soles from 26 percent up to 50 percent, which distinguishes over all known prior art; the earlier ""478 application specified thickness and density variations of up to 25 percent.
In addition, for shoe sole thickness deviating outwardly in a constructive way from the theoretically ideal stability plane, the shoe sole thickness variation of the applicant""s shoe soles is increased in this application from 51 percent to 100 percent, as measured in frontal or transverse plane cross sections.
This application similarly increases constructive density variations, as most typically measured in durometers on a Shore A scale, to include 26 percent up to 50 percent and from 51 percent to 200 percent. The same variations in shoe bottom sole design can provide similar effects to the variation in shoe sole density described above.
In addition, any of the above described thickness variations from a theoretically ideal stability plane can be used together with any of the above described density or bottom sole design variations. All portions of the shoe""sole are included in thickness and density measurement, including the sockliner or insole, the midsole (including heel lift or other thickness variation measured in the sagittal plane) and bottom or outer sole.
The above described thickness and density variations apply to the load-bearing portions of the contoured sides of the applicant""s shoe sole inventions, the side portion being identified in FIG. 4 of the ""819 Patent. Thickness and density variations described above are measured along the contoured side portion. The side portion of the fully contoured design introduced in the ""819 Patent in FIG. 15 cannot be defined as explicitly, since the bottom portion is contoured like the sides, but should be measured by estimating the equivalent FIG. 4 figure; generally, like FIGS. 14 and FIG. 15 of the ""819 Patent, assuming the flattened sole portion shown in FIG. 14 corresponds to a load-bearing equivalent of FIG. 15, so that the contoured sides of FIGS. 14 and FIG. 15 are essentially the same.
Alternately, the thickness and density variations described above can be measured from the center of the essential structural support and propulsion elements defined in the ""819 Patent. Those elements are the base and lateral tuberosity of the calcaneus, the heads of the metatarsals, and the base of the fifth metatarsal, and the head of the first distal phalange, respectively. Of the metatarsal heads, only the first and fifth metatarsal heads are used for such measurement, since only those two are located on lateral portions of the foot and thus proximate to contoured stability sides of the applicant""s shoe sole.
This major and conspicuous structural difference between the applicant""s underlying concept and the existing shoe sole art is paralleled by a similarly dramatic functional difference between the two: the aforementioned equivalent or similar thickness of the applicant""s shoe sole invention maintains intact the firm lateral stability of the wearer""s foot, that stability as demonstrated when the foot is unshod and tilted out laterally in inversion to the extreme limit of the normal range of motion of the ankle joint of the foot. The sides of the applicant""s shoe sole invention extend sufficiently far up the sides of the wearer""s foot sole to maintain the lateral stability of the wearer""s foot when bare.
In addition, the applicant""s shoe sole invention maintains the natural stability and natural, uninterrupted motion of the wearer""s foot when bare throughout its normal range of sideways pronation and supination motion occurring during all load-bearing phases of locomotion of the wearer, including when the wearer is standing, walking, jogging and running, even when the foot is tilted to the extreme limit of that normal range, in contrast to unstable and inflexible conventional shoe soles, including the partially contoured existing art described above. The sides of the applicant""s shoe sole invention extend sufficiently far up the sides of the wearer""s foot sole to maintain the natural stability and uninterrupted motion of the wearer""s foot when bare. The exact thickness and material density of the shoe sole sides and their specific contour will be determined empirically for individuals and groups using standard biomechanical techniques of gait analysis to determine those combinations that best provide the barefoot stability described above.
Finally, the shoe sole sides are made of material sufficiently flexible to bend out easily when the shoes are put on the wearer""s feet and therefore the shoe soles gently hold the sides of the wearer""s foot sole when on, providing the equivalent of custom fit in a mass-produced shoe sole. In general, the applicant""s preferred shoe sole embodiments include the structural and material flexibility to deform in parallel to the natural deformation of the wearer""s foot sole as if it were bare and unaffected by any of the abnormal foot biomechanics created by rigid conventional shoe sole.
At the same time, the applicant""s preferred shoe sole embodiments are sufficiently firm to provide the wearer""s foot with the structural support necessary to maintain normal pronation and supination, as if the wearer""s foot were bare; in contrast, the excessive softness of many of the shoe sole materials used in shoe soles in the existing art cause instability in the form of abnormally excessive foot pronation and supination.
Directed to achieving the aforementioned objects and to overcoming problems with prior art shoes, a shoe according to the ""714 invention comprises a sole having at least a portion thereof following the contour of a theoretically ideal stability plane, and which further includes rounded edges at the finishing edge of the sole after the last point where the constant shoe sole thickness is maintained. Thus, the upper surface of the sole does not provide an unsupported portion that creates a destabilizing torque and the bottom surface does not provide an unnatural pivoting edge.
In another aspect in the ""714 application, the shoe includes a naturally contoured sole structure exhibiting natural deformation which closely parallels the natural deformation of a foot under the same load. In a preferred embodiment, the naturally contoured side portion of the sole extends to contours underneath the load-bearing foot. In another embodiment, the sole portion is abbreviated along its sides to essential support and propulsion elements wherein those elements are combined and integrated into the same discontinuous shoe sole structural elements underneath the foot, which approximate the principal structural elements of a human foot and their natural articulation between elements. The density of the abbreviated shoe sole can be greater than the density of the material used in an unabbreviated shoe sole to compensate for increased pressure loading. The essential support elements include the base and lateral tuberosity of the calcaneus, heads of the metatarsal, and the base of the fifth metatarsal.
The ""714 application shoe sole is naturally contoured, paralleling the shape of the foot in order to parallel its natural deformation, and made from a material which, when under load and tilting to the side, deforms in a manner which closely parallels that of the foot of its wearer, while retaining nearly the same amount of contact of the shoe sole with the ground as in its upright state under load. A deformable shoe sole according to the invention may have its sides bent inwardly somewhat so that when worn the sides bend out easily to approximate a custom fit.
Directed to achieving the aforementioned objects and to overcoming problems with prior art shoes, a shoe according to the ""478 invention comprises a sole having at least a portion thereof following approximately the contour of a theoretically ideal stability plane, preferably applied to a naturally contoured shoe sole approximating the contour of a human foot. In the applicant""s shoe sole inventions, the shoe sole thickness of the contoured side portions are at least similar to the thickness of the sole portion directly underneath the foot, meaning either a thickness variation from 5 to 10 percent or from 11 to 25 percent, as measured in frontal or transverse plane cross sections.
In another aspect of the ""478 invention, the shoe includes a naturally contoured sole structure exhibiting natural deformation which closely parallels the natural deformation of a foot under the same load, and having a contour which approximates, but increases beyond the theoretically ideal stability plane. When the shoe sole thickness is increased beyond the theoretically ideal stability plane, greater than natural stability results; when thickness is decreased, greater than natural motion results.
In a preferred embodiment of the ""478 invention, such variations are consistent through all frontal plane cross sections so that there are proportionally equal increases to the theoretically ideal stability plane from front to back. That is to say, a 25 percent thickness increase in the lateral stability sides of the forefoot of the shoe sole would also have a 25 percent increases in lateral stability sides proximate to the base of the fifth metatarsal of a wearer""s foot and a 25 increase in the lateral stability sides of the heel of the shoe sole. In alternative embodiments, the thickness may increase, then decrease at respective adjacent locations, or vary in other thickness sequences. The thickness variations may be symmetrical on both sides, or asymmetrical, particularly since it may be desirable to provide greater stability for the medial side than the lateral side to compensate for common pronation problems. The variation pattern of the right shoe can vary from that of the left shoe. Variation in shoe sole density or bottom sole tread can also provide reduced but similar effects.
This invention relates to shoe sole structures that are formed to conform to the all or part of the shape of the wearer""s foot sole, either under a body weight load (defined as one body weight or alternately as any body weight force), but without contoured stability sides as defined by the applicant.
Still more particularly, this invention relates to variations in the structure of such soles using a theoretically ideal stability plane as a basic concept, especially including structures exceeding that plane.
Finally, this invention relates to contoured shoe sole sides that provide support for sideways tilting of any angular amount from zero degrees to 150 degrees at least for such contoured sides proximate to any one or more or all of the essential stability or propulsion structures of the foot, as defined below and previously.
These and other features of the invention will become apparent from the detailed description of the invention which follows.